The performance of zirconia nanoparticles (ZrO2 NPs) is critically dependent on their dispersion and stability. Effective control of NP dispersion is crucial for achieving a high refractive index, transparency, and exceptional mechanical properties in organic-inorganic hybrid films that incorporate ZrO2 NPs. In this study, we compared the crystalline properties and stability of ZrO2 NPs synthesized via two distinct methodologies: solvothermal synthesis using a zirconium isopropoxide isopropanol complex (ZII, Zr(OCH(CH3)2)4·(CH3)2CHOH) and sol-gel synthesis using zirconyl chloride octahydrate (ZC, ZrOCl2·8H2O). Both solutions exhibited precipitation, and the particles showed aggregation behavior. Despite being in a suspended state, the particles synthesized using the ZII precursor (T-ZrO2) exhibited hard-sphere behavior, distinct interparticle boundaries, and a tetragonal crystalline phase. However, the particles produced using the ZC precursor (A-ZrO2) were nearly amorphous without well-defined sizes and morphologies. Further, the hydroxyl end groups of both particle types were exchanged using a silane coupling agent (3-(trimethoxysilyl)propyl methacrylate, TMSPM) via hydrolysis and condensation reactions. The presence of the TMSPM groups on the surface of ZrO2 NPs afforded surface-modified TMSPM-T-ZrO2 with enhanced stability and prevented particle aggregation, thus maintaining the dispersion stability for up to one year under ambient conditions. The low surface energy and stabilization of the TMSPM-T-ZrO2 NPs were influenced by the tetragonal crystalline phase, which was conducive to surface modification using a silane coupling agent.